rectifiers, etc.
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| Define rectification. | The process of changing alternating current (AC) to pulsating direct current (DC). | ||||
| What are the 2 methods of rectification? | Self rectification; vacuum tube or solid state diode rectification. | ||||
| Which method of rectification is used in mobile radiography? | Self rectification | ||||
| How are rectifying systems connected? | They are connected between the secondary side of the x-ray transformer and the x-ray tube. | ||||
| What is the most commonly used type of semiconductor? | Silicon | ||||
| Define n-type silicon. | Silicon "doped" with arsenic that has an extra electron. (n stands for negative) | ||||
| P-type Silicon | Silicon that contains Gallium and is short of one electron. (P stands for positive) | ||||
| What device is used to test the competency of rectifiers? | Spinning top | ||||
| What is an oscilloscope? | Device used to test the timer in 3-phase, 12-pulse equipment. | ||||
| Why is arsenic called a "donor atom?" | Because it furnishes electrons. | ||||
| Why is gallium called an "acceptor atom?" | Because it can accept electrons. | ||||
| How many valence electrons are in a silicon atom? | 4 | ||||
| How many valance electrons are in gallium's outer shell? | 3 | ||||
| Silicon makes use of __________ bonding. | Covalent | ||||
| Where is the rectifier located within the x-ray circuit? | Between the secondary side of the x-ray transformer and the x-ray tube. | ||||
| What is the principle disadvantage of self-rectification? | Low heat-loading capacity | ||||
| T/F: With self-rectification, exposure factors (kV and mAs) must be limited to lower values than with full-wave rectification. | True | ||||
| Half-wave rectification is aka ? | One-pulse rectification | ||||
| What is the spinning top used for? | To test the competency of rectifiers with single-phase equipment. | ||||
| Diode | Rectifying semiconductor consisting of a p-type crystal with an n-type to form a p-n junction | ||||
| Thyristor | Silicon-controlled rectifier used for high-speed switching of primary high-voltage x-ray circuit. | ||||
| Thermionic emission | Ejection of electrons from surface of wire due to increased heat, causing an electron cloud | ||||
| Space charge cloud | Same as thermionic emission | ||||
| What is the main advantage of full-wave rectification? | The exposure time for any given technique is cut in half. | ||||
| Which is more efficient for producing x-rays: Single-phase or 3-phase power? | 3-phase | ||||
| Voltage ripple | A way to characterize voltage waveforms. | ||||
| Single-phase power has __% ripple. | 100% | ||||
| 3-phase, 6-pulse power produces __% ripple. | 13 - 25 | ||||
| 3-phase, 12-pulse power produces __% ripple. | 4 - 10 | ||||
| High-frequency generators have approximately __% ripple | 1% | ||||
| Note: | Less voltage ripple results in higher radiation quantity and quality | ||||
| Oscilloscope | Used to test the timer in 3-phase, 12-pulse equipment. | ||||
| What is the effective kVp with 12-pulse generators? | 95% | ||||
| What is the effective kVp with 6-pulse generators? | 87% | ||||
| Which type of rectification will supply the x-ray tube with the greatest power? | Full wave | ||||
| What is the maximum kVp produced by most 3-phase x-ray generators? | 150 | ||||
| To produce equal density and contrast, exposure to the patient with 3-phase equipment is ___ compared to single phase. | Equally | ||||
| To prevent shock, the secondary step-up transformer is __. | grounded | ||||
| Why are 3-phase generators more efficient than single-phase generators? | Voltage never drop to zero. | ||||
| Rectifier | Device allowing current flow in only one direction. | ||||
| Star and delta configurations are related to? | Three-phase transformers | ||||
| With 3-phase equipment, toe voltage across the x-ray tube is __ to __% of the maximum value and is nearly ___ potential. | 87 to 96%, constant | ||||
| What is the percentage of voltage ripple for a single-phase generator? | 100% voltage ripple | ||||
| A full-wave rectified, 3-phase, 6-pulse waveform produces approximately ____% more average photon energy than single phase. | 35 | ||||
| A full-wave rectified, 3-phase, 12-pulse waveform produces approximately ___% more average photon energy than single phase. | 40 | ||||
| Mobile units operate on _______________ battery-supplied AC current. | Nickel-cadmium |
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Created by:
rad1958tech
on 2008-03-07